the present invention is presently concerned, primarily, with nuclear steam generators. These units are designed and constructed with an excess of heat exchange tubing. When the inevitable leaks develop in the tubing it is practical to seal large numbers of the leaking tubes without reducing the capacity of the unit.
The present practice is to close down the complete system. The primary 111side of the steam generator is drained of water and the system cleaned of radioactive residue. The manways are opened for personnel to enter the primary side of the generator for repair.
The repair procedure is to plug off the defective tubes of both the inlet and outlet side of the tube-to-tubesheet joint. At present, a force-fit tube plug is driven into the end of the tube extended through its tubesheet. The plug is then manually seal-welded into place at the surface of the tubesheet. Obviously, the present practice requires personnel to drive the plug into place within the tube and manipulate the welding torch at the work area.
What is needed is a design for a tube plug which enables the plug to be virtually self-locating to obviate driving the plug into place within its tube. Further, manual manipulation of the plug should be eliminated and a positive stop provided to insure the proper depth for the plug to be positioned in the tube hole for proper welding.